There is a need to broaden current research models investigating the relationship between stress and cardiovascular (CV) function so that knowledge can be obtained regarding the role of environmental stress in the etiology of CV diseases. This will be accomplished by developing a model of social stress and CV response in different inbred strains of laboratory rats. This model will be developed by studying the effects of various types of social stress (including defeat, sexual behavior, social conduct, low social status, and achievement of high status through fighting) on CV response. The importance of social stress will be investigated by comparing the time course of CV response to defeat with the time course of CV response to other typical laboratory stressors (such as foot-shock) among inbred strains which are known to differ in their susceptibility to develop hypertension. Experiments will investigate the role of other social stressors, such as sexual behavior, and its interaction with agonistic conflict, the role of approach/avoidance conflict in a social context, and the development of CV response in rats living in a dynamic colony reared in a naturalistic environment. The role of social stability and social status achieved through aggression will be examined through studies conducted in naturalistic environments. Finally, in some experiments, the neuroendocrine consequences of stress exposure will be assessed by assay of tyrosine hydroxylase. These experiments should provide information stimulating future studies investigating specific mechanisms which account for CV alteration to exposure to social stress.